Hi there - hope this might help somewhat:

I used to be a pilot for a DL-affiliated Regional Airline, so had access to DL travelnet for benefits.

At my airline, we were not allowed to create logins for our travel beneficiaries. Basically, we had to play the role of travel agent. For someone employed by actual DL this may be different - I'm not sure, as I was with a DL regional. Most of the time I observed agents automatically rolling over standbys/non-revs to the next flight if multiple existed. If things were calm it was appropriate to approach the gate agent and ask for assistance, but if things were hectic/busy, that is frowned upon. Best to contact your son in that case.

I'm still an airline pilot - not DL affiliated - and I NEVER non-rev. To me it's not worth the hassle. I much prefer to buy a ticket and not chance it. Not trying to burst your bubble here, but non-revving is a risky game and not for those on tight schedules.